1232 



25 — 30", the allo-aeid was obtained in the melted condilion in the 

 presence of the crystals of the double acid). 



To portions of this solution crystals of the double acid were added, 

 which, in order to prevent infection by traces of allo-cinnamic acid, 

 had been waslied a few times with a little alcohol and then dried 

 between filter paper. If the double acids were diffei-ent. those which 

 had been formed in (he presence of acid of m.p. 58° and 68°, in 

 a solution in equilibrium with the acid of m.p. 42°, should have 

 brought about crystallisation of allo-cinnamic acid melting at 58° or 

 68° respectively and of the corresponding double acids. The experi- 

 ment showed, however, that this is not the case; the double acids 

 had no effect whatever on the solution, which proves them to be 

 identical. 



Similar experiments were carried out with a petrol solution pre- 

 pared by boiling for i hour a solution from which the double acid 

 and allo-cinnamic acid of m.p. 68° iiad crystallised, with an adequate 

 quantity of allo-cinnamic acid and the double acid. Next day the 

 solution had not crystallised, but it did so at once on shaking. After 

 standing for a few hours with occasional shaking the experiment 

 with the double acids was carried out, but here also no effect at 

 all was observed. The solution itself was found to crystallise at once 

 on inoculation with allo-cinnamic acid of m.p. 58° and 68°, and to 

 a very large extent, much more than the aqueous solution. It need 

 hardly be pointed out that in these experiments it is necessary to 

 guard against infection. 



After the stir created by Biit.mamn's well known paper in which 

 he first described the ready inter-conversion of the allo-cinnamic 

 acids and attributed it to trimorphism, various papers have appeared, 

 both from supporters and opponents of his views. ') The opponents 

 wish to regard the acids as chemical isomerides ; thus Stobbe and 

 Schönburg') write as the result of their elaborate investigation "dasz 

 die Alio- und Isozimmtsauren drei chemisch verschiedene Indivi- 

 duen sind." 



This conclusion cannot however be correct, since my experiments 

 prove the identity of the double acids of normal and of allo-cinna- 

 mic acids, formed in the presence of the allo-acids of m.p. 58° and 

 68° and in a solution in equilibrium with the acid of m.p. 42°. 

 For if the allo-cinnamic acids were chemically distinct there ought 

 also to be three different double acids with normal cinnamic acid. 



1) For literature references see Ann. 402, 187 (1913). 

 ») Ann. 402, 258 (1913). 



